This invention relates, in general, to manufacturing semiconductor products, and more particularly to etching features used in semiconductor devices for semiconductor products.
Generally, etching is a pattern transfer process that has been used in manufacturing semiconductor devices for a long time. Basically, the process requires that a masking layer be defined with a pattern. The masking layer is placed over or on top of a film that the pattern is to be transferred into. The film is then removed or etched away from around the masking layer, leaving an identical pattern that was previously defined by the masking layer in the etched film. Additionally, some features can also be fabricated by etching whole films without the use of the masking layer.
A large portion of etching of semiconductor devices is achieved conventionally by using gaseous plasma processes. These plasma processes are generally known as plasma etching. By selecting appropriate process conditions, the gaseous plasma can be made to be a predominantly chemical process, a predominantly physical process or a combination of both chemical and physical processes. Selecting either a predominantly chemical process or a predominantly physical process, results in different structural effects in the etched film. Chemical processes etch in an isotropic manner and do not exhibit dimensional control, whereas physical processes etch in an anisotropic manner and do exhibit dimensional control. Further, chemical or isotropic etching processes generally do not damage an underlying layer or a substrate which is beneath the layer that is being etched; however, anisotropic etching processes typically use high potential plasmas which do damage the underlying layer or substrate beneath the layer that is being etched.
Additionally, by adjusting the process conditions of the gaseous plasma, process parameters, such as etch rate and selectivity, can be adjusted and changed. Etch rate or removal rate is a parameter that indicates a speed at which a material is being removed. Selectivity is the etch rate or the removal rate of two or more materials that are compared to each other for a given set of plasma conditions. Until recently, adjustment of the gaseous plasma to either a predominantly chemical process or a predominantly physical process was sufficient to obtain desired results in regards to structural effects, etch rates, and selectivities.
However, as semiconductor products have become more complicated and etch requirements have become more stringent, several problems have occurred with achieving the desired selectivities, while maintaining desired structural effects. One problem occurs when a highly selective etch is required between two materials that etch at similar etch rates, and are etched simultaneously. By using conventional adjustment methods, it is not possible to etch these materials with high selectivity and with dimensional control. Not being able to achieve these requirements, makes it impossible to manufacture some structures or degrades the semiconductor device that are manufactured.
Additionally, problems of dimensional control and damage to an underlying layer or substrate are exacerbated when plasma etching of features with high aspect ratios, such as when fabricating sidewall spacers. By using conventional methods, it is not possible to etch features with high aspect ratios and still maintain dimensional control, high selectivity, and low damage to underlying structures.
Therefore, a method to achieve highly selective etches and to have a greater dimensional control would be very desirable. Additionally, having a method that protects the semiconductor device from radiation damage or etch damage from energetic ions would also be desirable.